Add greenkeeper-lockfile

Add `greenkeeper-lockfile` so _theoretically_ Greenkeeper will also keep
the lockfile updated.

Author: Arcanemagus

.circleci/config.yml

@@ -26,12 +26,26 @@ jobs:
           # fallback to using the latest cache if no exact match is found
           - v1-dependencies-
 
+      # Print some information
+      - run: node --version
+      - run: npm --version
+
+      # Install greenkeeper-lockfile
+      - run: sudo npm install -g greenkeeper-lockfile@latest
+
+      # Install the dependencies
       - run: npm install
 
+      # Update the lockfile with greenkeeper
+      - run: greenkeeper-lockfile-update
+
       - save_cache:
           paths:
             - node_modules
           key: v1-dependencies-{{ checksum "package.json" }}
 
       # run tests!
       - run: npm test
+
+      # Upload the lockfile
+      - run: greenkeeper-lockfile-upload